Recently, due to the environmental concerns, usage of natural energy such as solar power generation and wind power generation, developing new energy such as fuel battery, and energy saving including cars and home electronics are actively promoted. It is an important matter to reduce energy consumption and power consumption in the future in Japan and all over the world. It is considered that one of the solutions is “visualizing power consumption” of each electric equipment and electronic device, and realizing strengthening the management and control function of power charge and power consumption.
In a circumstance where internet and so on can be utilized in recent years, development of a power management system including remote meter reading of electricity meters has been progressed. Recently, measurement of macro power consumption of entire houses and factories and so on is performed, such as multiplication operation by a microprocessor or an electric circuit by adding a sensor for measuring rotations of an existing accumulating power meter or newly adding an ammeter (CT) or a power meter (PT).
However, these measurement apparatuses may be large and expensive, and useless energy may be consumed. Further, it is difficult to add a new measurement apparatus to existing equipment taking the vacant space of the existing equipment which is thickly designed and manufactured recently into consideration. Therefore, it is desired to develop smaller and more integrated power sensing devices.
To measure power, a meter accumulating electric energy, called a power meter or an informal meter is used. The most accessible one is induced type electric energy meter. This uses a disk of Arago. The disk made of aluminum is set to rotate with a speed proportional to the power, and the electric energy is measured by accumulating the rotation speed. However, such electric meter is too large to measure power consumption at a desired point of an electric circuit
In Patent Literature 1, an apparatus which measures power using a magnetic sensor utilizing a magnetoresistance effect is disclosed. The magnetic sensor detects current utilizing a magnetic film, and thus, it is considered to be possible to mount the magnetic sensor on a relatively small circuit.
Further, the power meter of Patent Literature 1 measures voltage and current separately and operate them. However, in Patent Literature 2, a power meter measuring power only measuring voltage between both terminals of a magnetic sensor utilizing a magnetoresistance effect. In either case, if it is possible to manufacture small magnetic sensor utilizing magnetoresistance effect, the possibility to measure power consumption at a desired point occur.
The magnetoresistance effect is a phenomenon that an electric resistance varies depending on a magnetic field applied from outside. This phenomenon occurs by variation of a direction of a current flowing in a magnetic film and a magnetization direction formed in the magnetic film. Therefore, with regard to the magnetic field from outside, the magnetoresistance effect has a character of even function. Accordingly, to obtain linearity, it is necessary to apply a bias magnetic field on some level in advance in a direction same as that of the magnetic field from outside.
This may be a factor which makes it difficult to downsize the magnetic sensor. However, Patent Literature 1 discloses a magnetoresistance effect element which can use a linear portion of the magnetoresistance effect without apparently applying any bias magnetic field by locating barber-pole electrodes on the magnetic film. FIG. 12 shows a structure of the magnetoresistance effect element 100 on which the barber-pole electrodes are located.
A magnetic film 112 having a strip shape is normally formed on a substrate 111. A magnetization easy axis EA is induced in a longitudinal direction of the strip shape in the magnetic film 112. Permalloy, which is a composition metal of iron and nickel, is preferably used for the magnetic film 112, for example. Electrodes called barber-pole electrodes 114 are formed on this magnetic film 112. The barber-pole electrodes 114 have inclined sides 114p with regard to the longitudinal direction of the strip shape and are belt-like films having superior electric conductivity. The material is formed of copper, zinc, nickel, aluminium, silver or a composition metal of these.
In these barber-pole electrodes 114, when current I2 flows between connection electrodes 116a and 116b at both sides of the magnetoresistance effect element 100, current flows from one inclined side 114p to another inclined side 114p. Then, the current I2 flows in a direction different from the longitudinal direction (magnetization direction of the magnetic film 112) of the stripe-shaped magnetic film 112, and thus, it is possible to use the linear portion of the magnetoresistance effect without any bias.